Replace custom EventTarget toNative call with [ToNativeArg] extended attribute

Source/core/events/EventTarget.idl

Index: Source/core/events/EventTarget.idl
diff --git a/Source/core/events/EventTarget.idl b/Source/core/events/EventTarget.idl
index 7febedfcedc843658d302a0918b9c8853da896d5..2b52d6500b77b2e3f874d80843f2e8f0cdcbe4d0 100644
--- a/Source/core/events/EventTarget.idl
+++ b/Source/core/events/EventTarget.idl
@@ -22,10 +22,10 @@
     Custom=ToV8,
 ] interface EventTarget {
     void addEventListener([TreatNullAs=NullString] DOMString type,
-                          EventListener listener,
+                          [ToNativeArg=ListenerFindOrCreate] EventListener listener,
                           optional boolean useCapture);
     void removeEventListener([TreatNullAs=NullString] DOMString type,
-                             EventListener listener,
+                             [ToNativeArg=ListenerFindOnly] EventListener listener,
                              optional boolean useCapture);
     [RaisesException] boolean dispatchEvent(Event event);
 };